Microbial structure and activity of UASB granules treating different wastewaters

Abstract

The microstructure of three types of UASB granules respectively treating sucrose, glutamate and brewery wastewaters in mesophilic conditions were analyzed by light, scanning electron and transmission electron microscopies, along with the specific methanogenic activity (SMA) of the granules. Results showed that the granule's microstructure was dependent on the nature of the substrate. Those degrading soluble carbohydrates exhibited a layered structure, while those degrading glutamate exhibited a rather uniform structure. Such a difference was explained based on the substrate's rates of acidogenesis and diffusion. A model of the typical layered structure was proposed. In addition, the acetoclastic Methanothrix was found as the key structural element in all the granules, suggesting that it plays an important role in granulation. Three types of syntrophic microcolonies were found to be abundant in granules degrading soluble carbohydrates: two were juxtapositioned syntrophic microcolonies, each was composed of hydrogen-producing acetogens and hydrogen-consuming methanogens, while the third was a cluster-type of syntrophic association between two microcolonies. The SMA data using individual VFA as substrate provided supporting evidence to the observations of the bacterial compositions in the granules.

A simplified analysis of granule behavior in ASBR and UASB reactors treating low-strength synthetic wastewater

“…This m ay be directly related to the differences observed in the granules. Fang et al (1994) verified that acetoclastic Methanosaeta were the key structural granules from UASB reactor treating different substrates. Filamentous microorganisms and Methanoseata-like cells seem to have a structural role, producing stability of the pellets formed.…”

Celebrating 40 years anaerobic sludge bed reactors for industrial wastewater treatment

“…As a result, the insight in the mechanism of the sludge granulation process for anaerobic treatment has been elucidated sufficiently, at least for practical application (e.g. De Zeeuw 1982Hulshoff Pol and Lettinga 1986;Wiegant and de Man 1986;Hulshoff Pol et al 1987Dolfing 1987;Wu et al 1991;van Lier et al 1994;Fang et al 1994;Liu et al 2003;Song et al 2010;Habeeb et al 2011;Abbasi and Abbasi 2012;Subramanyam 2013). Granulation can proceed under mesophilic, thermophilic and psychrophilic conditions.…”

“…Similar findings have been reported in the study of Baloch et al (2008), in which anaerobic granules were found to possess a multi-layered structure with complex microbial ecology and dominating methanogenic subpopulations. Apparently, Methanosaeta plays an important role in sludge granulation (Fang et al 1994). The structured characteristics and layered 'ecological zones' of the granules were defined as a stable metabolic arrangement that creates optimal nutritional and environmental conditions for all microorganisms included in it (Guiot et al 1992).…”

“…The structured characteristics and layered 'ecological zones' of the granules were defined as a stable metabolic arrangement that creates optimal nutritional and environmental conditions for all microorganisms included in it (Guiot et al 1992). The carbon source or substrate was considered the most important factor affecting the microstructure of the UASB granules (Grotenhuis et al 1991;Fang et al 1994;Batstone et al 2004). The extent of required acidification and the acidogenesis rate of the substrate affects the concentration profiles of the substrate, metabolites in the granule and its structure.…”

A review on characterization and bioremediation of pharmaceutical industries’ wastewater: an Indian perspective

“…This reactor has been successfully applied for high-rate anaerobic wastewater treatment. The success of UASB depends on the formation of active and able granules (Fang et al 1994). These granules consist of self-immobilized, compact form of aggregate of organisms and lead to an effective retention of organisms in the reactor (Akunna and Clark 2000).…”